The present invention relates generally to patient temperature management using internal heat exchange.
The present assignee""s U.S. patent application Ser. No. 09/220,897, now U.S. Pat. No. 6,146,411, discloses a cooling system for controlling the temperature of coolant that is circulated through a heat exchange catheter such as that disclosed in the present assignee""s co-pending U.S. patent application Ser. No. 09/253,109, now abandoned, both of which are incorporated herein. This application discloses a control method for establishing the temperature of the water bath in the cooling system.
A controller for a heat exchanger that heats and cools saline flowing through a closed loop heat exchange catheter cools the saline to achieve a target temperature, and then immediately upon reaching target temperature heats the saline. Upon detection of, e.g., a slight patient temperature rise, the controller cools the saline again, with the control loop continuing to tightly control patient temperature in a narrow band around the target temperature.
Accordingly, in one aspect a method for managing patient temperature includes advancing a cooling catheter into a patient. The cooling catheter includes an internally circulating coolant communicating with a heat exchanger. The method includes establishing a target temperature, receiving a patient temperature signal, and causing the heat exchanger to reduce the temperature of the coolant until target temperature is reached. Then, the method includes immediately raising the temperature of the coolant.
In a preferred embodiment, the temperature of the coolant is next lowered in response to receiving an indication that heat exchange should reverse. And again, the temperature of the coolant is raised in response to receiving an indication that heat exchange should reverse.
In another aspect, a system for managing patient temperature to be within a range of a target temperature includes a heat exchange catheter advanceable into a patient, and a heat exchanger. A coolant circulation path is between the catheter and heat exchanger. A controller establishes a temperature in the heat exchanger based at least in part on a sensed patient temperature and a target temperature, with the controller causing the heat exchanger to lower coolant temperature until target temperature is reached and then causing the heat exchanger to immediately raise coolant temperature. In a preferred embodiment, the heat exchanger includes a water bath, and the coolant is in thermal contact with the bath. Also in the preferred embodiment, a heat transfer unit through which coolant flows is disposable in the bath.
The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which: